Ann: OTTO PROVIDES UPDATE ON TIMETABLE FOR RETURN OF CAPITAL, page-73

You only realise a CGT event when you sell the security. So, as per my understanding as an Australian resident, you don't declare the capital return. When you sell the security you reduce the purchase amount by the cap return amount and the sale and purchase date being one year apart determines if CGT eligible.

So for example

Bought OEL for 1.3 cents today 4 April, receive 0.8 cents cap return in August (for arguments sake), sell for 0.7 cents on 5 April 2025, you are eligible for CGT discount on CG of 0.2 cents (=0.7-(1.3-0.8))